Cryptomeria japonica D. Don is a coniferous tree species widely grown in southern China for its high ornamental value. Recently, during disease surveys in China, a symptom of dieback occurred on C. japonica in Nanjing, Jiangsu Province, China. A total of 130 trees were surveyed and more than 90% showed the same symptom. The crowns of affected trees were brown when viewing from a distance, and the bark showed no difference from the healthy ones. In this study, 157 isolates were isolated from the 3 affected plants of C. japonica, and based on the living culture on PDA, the fungal isolates were preliminarily divided into 6 groups. Thirteen representative isolates were selected for the pathogenicity test, and seven of them showed obvious pathogenicity on C. japonica, causing stem basal canker. These isolates were identified based on comparisons of the DNA sequences of the internal transcribed spacer regions (ITS), partial translation elongation factor 1-alpha (tef1), β-tubulin (tub2), and DNA-directed RNA polymerase II subunit (rpb2) and combined with their morphological characteristics. Results showed that these seven isolates belong to two taxa in Neofusicoccum, including a species new to science. The new species, Neofusicoccum cryptomeriae, was hereby described and illustrated. The other species was N. parvum. Both species were pathogens of stem basal canker of Cryptomeria japonica.

Viburnum odoratissimum Ker-Gawl is native to Asia and is usually used as a garden ornamental. In September 2022, a leaf blotch on V. odoratissimum was observed in Nanjing, Jiangsu, China. The disease causes the leaves of the plants to curl and dry up and defoliate early. It not only seriously affects the growth of the plants but also greatly reduces the ornamental value. The pathogenic fungus was isolated from the diseased leaves, and the fungus was identified to be Colletotrichum siamense based on morphological features and multilocus phylogenetic analyses of the internal transcribed spacer (ITS) region, actin (ACT), calmodulin (CAL), beta-tubulin 2 (TUB2), chitin synthase (CHS-1), Apn2-Mat1-2 intergenic spacer and partial mating type (ApMat), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes. Pathogenicity tests were performed by inoculating healthy leaves with conidia. C. siamense can grow at 15–35 °C, with an optimal growth temperature at 25–30 °C. The results of sensitivity to nine fungicides showed that C. siamense was the most sensitive to prochloraz in the concentration range of 0.01 μg/mL to 100 μg/mL. Therefore, spraying prochloraz before the optimum growth temperature of pathogenic fungus can achieve effective control. It provided useful information for future studies on the prevention and treatment strategies of C. siamense. This is the first report of leaf blotch caused by C. siamense on V. odoratissimum in China and worldwide.

Celtis julianae Schneid. is widely planted as a versatile tree species with ecological and economic significance. In September 2022, a leaf blotch disease of C. julianae was observed in Nanjing, Jiangsu, China, with an infection incidence of 63%. The disease led to severe early defoliation, significantly affecting the ornamental and ecological value of the host tree. The accurate identification of pathogens is imperative to conducting further research and advancing disease control. Koch’s postulates confirmed that the fungal isolates (B1–B9) were pathogenic to C. julianae. The morphology of the characteristics of the pathogen matched those of Alternaria spp. The internal transcribed spacer region (ITS), large subunit (LSU) and small subunit (SSU) regions of rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen gene (Alt a 1), RNA polymerase second largest subunit (RPB2), and portions of translation elongation factor 1-alpha (TEF1-α) genes were sequenced. Based on multi-locus phylogenetic analyses and morphology, the pathogenic fungi were identified as Alternaria arborescens and A. italica. The findings provided useful information for disease management and enhanced the understanding of Alternaria species diversity in China. This is the first report of A. arborescens and A. italica causing leaf blotch of C. julianae in China and worldwide.

Celtis sinensis is a highly versatile species that is commonly cultivated in the southern regions of China. In June 2022, leaf spot disease was detected in C. sinensis in Nanjing, Jiangsu, China. Based on morphological characteristics, three isolates were determined to be of the Alternaria species. A phylogenetic analysis of combined ITS, GAPDH, TEF1-α, RPB2, and Alt a 1 sequences identified the three isolates we obtained as Alternaria alternata and A. koreana. We determined the pathogenicity of A. alternata and A. koreana in C. sinensis leaves using inoculation through in vivo experiments. Symptoms of inoculation onset in indoor pots were in accordance with those observed in the open country. A. alternata and A. koreana can grow at 15–35 °C, with the best growth occurring at 25 °C. The findings from fungicide susceptibility experiments demonstrated that A. alternata and A. koreana were the most sensitive to prochloraz, which could offer an effective approach for future prevention and control measures against A. alternata and A. koreana. This study provides the initial step toward further research on A. alternata and A. koreana as pathogens of C. sinensis and provides the stage for future control strategy development.

Celtis sinensis is an adaptable species that is widely grown in southern China. In June 2022, a leaf blotch disease of C. sinensis was observed in Nanjing, Jiangsu, China. Based on morphological characterization, three isolates were identified as Alternaria species. Phylogenetic analysis of combined ITS, GAPDH, TEF1-α, RPB2 and Alt a 1 sequences identified the three isolates we obtained as Alternaria alternata and Alternaria koreana. Koch’s postulates were fulfilled in the greenhouse, and the pathogenicity of A. alternata and A. koreana was determined by leaf inoculation tests on C. sinensis seedlings. The symptoms of indoor inoculation were consistent with those in the field. A. alternata and A. koreana can grow at 15-35 °C, with an optimal growth temperature of 25 °C. The results of fungicide sensitivity experiments indicated that A. alternata and A. koreana were the most sensitive to prochloraz, which may be a useful strategy for the future prevention and control management of A. alternata and A. koreana. This study provides the first step for further research on A. alternata and A. koreana as pathogens of C. sinensis and provides a theoretical basis for future control strategies.